The present invention relates to an injection timing control device for an internal combustion engine and, more particularly, to an improvement in a hydraulically operated injection timing control device.
A prior art injection timing control device of the type described includes a disc and a cam support plate which is mounted on a shaft and connected to the disc by an eccentric cam mechanism. One of the disc and shaft is connected to a shaft of a fuel injection pump, and the other to a crankshaft of an engine. A hydraulic actuator surrounds the shaft associated with the cam support and includes cylinders. A pair of generally U-shaped connector plates are arranged one above the other between the cylinders and the cam support straddling the shaft and are movable relative to each other. Opposite ends of each connector plates are bent perpendicular to the general plane of the plate to form a pair of tongues. A guide rod extends throughout the adjacent tongues of the two connector plates. A return spring is loaded between each end of the guide rod and one of the tongues which faces the rod end. The connector plates are individually connected by pins to the eccentric cam mechanism mounted in the cam support and to pistons installed in the hydraulic actuator.
The problem encountered with the prior art injection timing controller described above is that cams included in each eccentric cam mechanism are apt to become locked in position to prevent the injection timing from being adjusted smoothly and stably. The inherent construction allows a moment to act in one direction on each connector plate, tending to cause the connector plate to tilt. This tendency is increased by clearances defined at both sides of the connector plate. When the connector plate is tilted, the eccentric cam mechanism associated therewith is also tilted allowing slidable members of the mechanism to catch each other. Another problem brought about by such a tendency of the connector plates is that the eccentric cam mechanisms are locally worn out to limit the durability of the whole device.
The present invention constitutes an improvement over the prior art hydraulically operated injection timing control device described above.